French and Belgian courts have seized Russian government assets in three countries in an effort to repay shareholders of Yukos, the now defunct Russian oil company.
The Kremlin said it was looking into the seizure of state property, with one minister saying it would be unfriendly while another said it would be illegal. The Foreign Ministry said it is considering measures against Belgium.
It comes after an international arbitration court ruled last July that Russia must pay out more than 40 billion euros for expropriating the assets of Yukos.
The company was broken up and nationalised in 2003 when owner Mikhail Khodorkovsky was arrested on fraud and tax evasion charges. Moscow then auctioned off its assets, most of which ended up in the hands of state oil giant Rosneft.